A Consolidated Grant in Astrophysical Fluids In Applied Mathematics at Leeds

Lead Research Organisation: University of Leeds
Department Name: Applied Mathematics

Abstract

Many astrophysical phenomena involve the complex interaction between magnetic fields, rotation and fluid flows. We intend to undertake a systematic and integrated programme of research to investigate this complex interaction in a wide variety of astrophysical objects. We shall utilise a combination of analytical and numerical techniques (including the application of cutting edge numerical algorithms optimised for use on massively parallel machines) to gain an understanding of such phenomena. Our unifying philosophy is to investigate the underlying fundamental physical interactions in these astrophysical fluids and to use expertise gained in one area in order to make progress on different objects that have the same underlying physical structures. The physical phenomena that we shall address are:

(1) The generation of magnetic fields in the Sun, including the formation of the well-known eleven year sunspot cycle.
(2) The formation of sunspots and the link with the magnetic fields in the solar corona.
(3) The generation of magnetic fields in planets.
(4) The evolution of planetary orbital dynamics and the importance of tidal effects.
(5) The decay of magnetic fields and the thermal structure of neutron stars.
(6) The dynamics of relativistic jets.

Planned Impact

There is particular impact of the research into the origins and consequences of solar magnetic activity that is valuable to NASA in formulating its predictions of future solar magnetic activity via its solar prediction panel. In recognition of this, SMT was invited to act as a consultant for the previous NASA prediction panel; the research described in the solar projects will continue to inform NASA as the cycle progresses, and will feed into future predictions of magnetic activity.

NASA's mandate is to build, fly and operate spacecraft in the hostile environment of space. In order to carry this out successfully, it is necessary for NASA to anticipate the orbital decay of spacecraft (including Hubble) that arises from orbital drag and the need for reboosting. Moreover it must assess radiation hazards in order to design orbits. Both orbital drag and radiation depend on the level of solar activity and so an accurate long-term forecast of solar activity is vital. To this end, NASA has constituted a solar cycle prediction panel in order to predict the level and date of the next solar maximum. The results of this prediction are utilised by a number of end-users including satellite builders and operators and policy-makers.

As a consultant to the panel, SMT has utilised the research conducted at the University of Leeds to detail the lack of predictability of the dynamo models that predicted a high level of activity. The research had shown that the inherently nonlinear nature of the dynamo equations, together with uncertainties over the size and even sign of the transport coefficients in the models, make prediction impossible. In the light of these results, the panel split its initial forecast with half forecasting a high cycle and half a low cycle (based on timeseries predictions). As the solar cycle has progressed (up to 2011), the panel has met several times and has gradually revised its forecast downwards. Most current forecasts predict an exceptionally low level of activity at the next solar maximum, which corroborates the Leeds group's research casting doubt on dynamo predictors. As a result of the research, focus has now turned to data assimilation methods for prediction. NASA make their predictions publicly available through the site: http://solarscience.msfc.nasa.gov/predict.shtml

We shall exploit the results of the solar physics research in the proposal (projects 1,2,3) in our continued consultations with members of the NASA prediction panel. In particular, the research into the dynamics of the tachocline and into the formation of active regions will have implications for future predictions of magnetic activity; we shall continue to advise the NASA prediction panel of the consequences of these implications. Moreover, the UK has a vibrant satellite sector and this is evidenced by the Technology Strategy Board's recent decision to invest millions in a centre to support the UK satellite industry. The Astrophysical Fluid Dynamics and MHD group is aware of the TSB's recent announcement that it will support a Catapult centre for the UK satellite industry and proposes to engage with the centre to make its advice more readily available to the industry.

In general, the research performed by members of the group also has significant impact via our outreach, whereby members of the group often give talks in schools.

Publications

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Acevedo-Arreguin L (2013) Dynamics of the solar tachocline - III. Numerical solutions of the Gough and McIntyre model in Monthly Notices of the Royal Astronomical Society

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Bamford J. T. (2018) The reconfinement of AGN jets in arXiv e-prints

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Barkov Maxim V. (2016) Relativistic tearing and drift-kink instabilities in two-fluid simulations in Monthly Notices of the Royal Astronomical Society

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Bowker J (2014) Incorporating velocity shear into the magneto-Boussinesq approximation in Geophysical & Astrophysical Fluid Dynamics

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Cattaneo F (2014) ON LARGE-SCALE DYNAMO ACTION AT HIGH MAGNETIC REYNOLDS NUMBER in The Astrophysical Journal

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Child A (2015) Nonaxisymmetric linear instability of cylindrical magnetohydrodynamic Taylor-Couette flow. in Physical review. E, Statistical, nonlinear, and soft matter physics

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Child A (2017) Axisymmetric pulse train solutions in narrow-gap spherical Couette flow in Physica D: Nonlinear Phenomena

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CĂ©bron D (2014) TIDALLY DRIVEN DYNAMOS IN A ROTATING SPHERE in The Astrophysical Journal

 
Description This award has made significant progress in furthering our understanding of the generation of magnetic fields in the Sun (leading to the solar activity cycle) and other solr system planets. In addition it has made breakthroughs in our understanding of the behaviour of neatron stars and nebulae.
Exploitation Route The findings will be of use to the aerospace and satellite industry in terms of space weather prediction.
Sectors Digital/Communication/Information Technologies (including Software),Education

URL http://www.leeds.ac.uk/news/article/3402/researchers_reveal_model_of_suns_magnetic_field
 
Description Professor S.M. Tobias was interviewed on the Today Programme on Radio 4 about solar magnetic activity. He was also a consultant for the NASA solar cycle prediction panel (2008)
First Year Of Impact 2013
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software)
Impact Types Cultural,Societal,Economic

 
Description Astrophysics of Crab Nebula 
Organisation Catholic University of Louvain
Department Department of Mathematics
Country Belgium 
Sector Academic/University 
PI Contribution Theoretical investigation of Pulsar Wind Nebulae and Astrophysical jets. Computer simulations.
Collaborator Contribution The computer code ARMVAC and technical assistance with its utilization.
Impact Numerous publications
Start Year 2012
 
Description Astrophysics of Crab Nebula 
Organisation Purdue University
Department Department of Physics and Astronomy
Country United States 
Sector Academic/University 
PI Contribution Theoretical investigation of Pulsar Wind Nebulae and Astrophysical jets. Computer simulations.
Collaborator Contribution The computer code ARMVAC and technical assistance with its utilization.
Impact Numerous publications
Start Year 2012
 
Description Stability of astrophysical jets 
Organisation University of Notre Dame
Department Department of Physics
Country United States 
Sector Academic/University 
PI Contribution Joint study of the jet stability problem
Collaborator Contribution Joint study of the jet stability problem
Impact Joint publication in a scientific journal.
Start Year 2015
 
Description poular science article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? Yes
Type Of Presentation Paper Presentation
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Article Porth, Keppens, "In the heart of the Crab Nebula"
september issue 2013, pages 106-109 ( in dutch).

Wider dissemination of our results
Year(s) Of Engagement Activity 2013